The invention relates to a magnetic tunnel junction device provided with a multilayer structure including a pair of electrode layers of a ferromagnetic material and an interposed tunnel barrier layer of insulating material.
Such a device is known from U.S. Pat. No. 5,650,958. The known device has two ferromagnetic electrode layers and an insulating tunnel barrier layer located between and in contact with both ferromagnetic layers. The insulating layer is thin enough to allow quantum mechanical tunneling between the electrode layers. The known tunnel junction device demonstrates a better magnetoresistance response than anisotropic magnetoresistive devices or giant magnetoresistive devices It is known per se from e.g. the article "Generalized Formula for the Electric Tunnel Effect between Similar Electrodes Separated by a Thin Insulating Film", Journal of Applied Physics, Volume 34, number 6, June 1963, pages 1793-1803, John C. Simmons, that the tunnel resistance of a device, that includes two electrodes separated by a thin insulating film, depends on the thickness of the insulating film and the value of the tunnel barrier height. In order to guarantee electric and magnetic insulations between the two electrodes, a certain minimal thickness of the insulating film is required. The barrier height is physically determined by the combination of electrode material and insulating film material.
The above citations are hereby incorporated herein in whole by reference.
The inventors recognize that in the known tunnel junction device, the tunnel junction resistance is relatively high and thereby has a restricted current-voltage characteristic.